The present disclosure relates to identifying host computer systems. To establish a session between two separate nodes in a communication network, a first node, represented by a first identifier, may transmit one or more initial startup messages to a desired endpoint node. The desired endpoint node can initiate the session by responding to the startup message with a responder message. In some cases, however, a pre-existing session may already have been established with a second node, represented by a second identifier, in which the desired endpoint node and second nodes correspond to the same host.